An international team of researchers has detected an unexpectedly high abundance of organic molecules in the ultra-luminous infrared galaxy IRAS 07251-0248, bolstering the theory that the building blocks of life originated in space. The findings, based on data from the James Webb Space Telescope (JWST), reveal a complex chemical inventory in both gaseous and solid form within the galaxy’s nucleus.
IRAS 07251-0248 is particularly difficult to study with conventional telescopes because its central supermassive black hole (SMBH) is obscured by vast amounts of gas and dust. However, JWST’s infrared capabilities allow it to penetrate this dust, revealing unique information about the chemical processes occurring in the core region. The research, conducted by a team from the Consejo Superior de Investigaciones Científicas (CSIC) and multiple universities, utilized JWST’s Near-Infrared Spectrometer (NIRSpec) and Mid-Infrared Instrument (MIRI) to characterize the abundance and temperature of various chemical species.
The team identified hydrocarbons – fundamental building blocks of complex organic chemistry – including methyl radical (CH₃), benzene (C₆H₆), methane (CH₄), acetylene (C₂H₂), diacetylene (C₄H₂), and triacetylene (C₆H₂). These molecules were detected in a gaseous state, alongside a significant presence of organic matter in solid form, such as carbonaceous grains and water ices. “We found an unexpected chemical complexity, with abundances far higher than predicted by current theoretical models,” said CAB researcher and lead author Dr. Ismael García Bernete, as reported by the University of Oxford. “This indicates that there must be a continuous source of carbon in these galactic nuclei fuelling this rich chemical network.”
While minor organic molecules are not present in living cells, they are considered vital in prebiotic chemistry, representing a potential step towards the formation of amino acids and nucleotides, according to co-author Professor Dimitra Rigopoulou from the University of Oxford. The team’s analysis was supported by theoretical models of polycyclic aromatic hydrocarbons (PAHs) developed by Oxford researchers.
The researchers propose that the organic molecules are released in gaseous form through the fragmentation of PAHs and carbon-rich dust grains caused by cosmic-ray exposure. This explanation aligns with the prevalence of cosmic rays in active galactic nuclei (AGNs) and is supported by studies of similar galaxies that show a correlation between hydrocarbon abundance and cosmic-ray ionization intensity. The findings suggest that dusty galactic nuclei actively produce organic molecules, contributing to the chemical evolution of galaxies.
Recent discoveries have also revealed amino acids in asteroids and fatty acids on Mars, while sulfur-bearing molecules have been found in interstellar space, and peptides have been shown to form spontaneously in space. The James Webb Space Telescope has also recently scanned asteroid 2024 YR4, determining it to be 60 meters across, and revealed that asteroids Bennu and Ryugu may be fragments of the same larger space rock. These findings, combined with the new data from IRAS 07251-0248, demonstrate JWST’s ability to explore previously inaccessible environments and offer new opportunities for studying the formation and processing of organic molecules in extreme conditions, potentially leading to a better understanding of how galaxies become seeded with the ingredients for life.
